Organic carbon sequestration potential of Slovenian agricultural soil and the impact of management practices on SOC stock

Improving soil management is crucial for mitigating climate change by increasing soil organic carbon (SOC). This study addresses the question of whether Slovenian agricultural soils can increase SOC stocks and achieve the 4per1000 initiative (4p1000.org). We calculated the SOC stocks, soil carbon sequestration (SCS) potential of the fine soil fraction (sd) and the SCS potential of bulk soil for different agricultural uses in Slovenia. In addition, we conducted agricultural land management scenarios to determine a possible increase in SOC stocks. The results showed an average SOC stock of 94.7 t ha−1 in the agricultural soils of Slovenia. High Csd values were mainly found in croplands, intensive orchards and vineyards. The Csd (0–30 cm) amounts to 16.3 Mt SOC for the entire country. In addition, our results on SCS potential were compared with similar assessments from other European countries, where the range of bulk soil SCS potential was between 0.03 and 2.8‰ SOC change yr−1. With the current management of agricultural land in Slovenia, the SCS is almost balanced (+0.1‰). Different management scenarios showed that efficient fertilizer use, no-till, vegetation cover with biodiverse crop rotation and keeping residues on the surface lead to a significant SOC stock increase by 19.6 t ha−1 in 20 years, which supports the 4per1000 initiative target (10.5‰).

通过提升土壤有机碳（Soil Organic Carbon, SOC）储量以缓解气候变化，优化土壤管理至关重要。本研究旨在探究斯洛文尼亚农业土壤能否提升SOC储量，并达成千分之四倡议（4per1000 initiative，4p1000.org）的目标。本研究针对斯洛文尼亚不同农业用地类型，计算了SOC储量、细土粒组分（fine soil fraction, sd）的土壤碳固存（Soil Carbon Sequestration, SCS）潜力，以及全土的土壤碳固存潜力。此外，本研究设置了农业土地管理情景，以测算SOC储量的潜在提升空间。研究结果显示，斯洛文尼亚农业土壤的平均SOC储量为94.7吨/公顷（t ha⁻¹）。细土粒组分碳固存量（Csd）较高的区域主要集中于农田、集约化果园与葡萄园。全国范围内（0~30厘米土层）的Csd总量达16.3百万吨SOC。此外，本研究将土壤碳固存潜力的测算结果与欧洲其他国家的同类评估进行了对比，后者的全土土壤碳固存潜力区间为0.03~2.8‰ SOC·年⁻¹。按照斯洛文尼亚当前的农业土地管理模式，其土壤碳固存量基本处于平衡状态（增幅仅为+0.1‰）。不同管理情景的测算结果表明：优化肥料施用、采用免耕模式、实施生物多样性作物轮作并保留地表作物残体，可在20年内使SOC储量提升19.6吨/公顷，这一结果契合千分之四倡议设定的10.5‰目标。